A novel negative regulatory factor for nematicidal Cry protein gene expression in Bacillus thuringiensis |
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Authors: | Yu Ziquan Bai Peisheng Bai Peisheng Ye Weixing Zhang Fengjuan Ruan Lifang Yu Ziniu Sun Ming |
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Institution: | State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University,Wuhan 430070, Hubei, P.R. China. |
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Abstract: | A 3-kb HindIII fragment bearing the cry6Aa2 gene and the adjacent and intergenic regions was cloned from Bacillus thuringiensis strain YBT-1518. Two open reading frames (ORFs), namely, orf1 (termed cry6Aa2) and orf2 that were separated by an inverted-repeat sequence were identified. orf1 encoded a 54-kDa protein that exhibited high toxicity to the plant-parasitic nematode Meloidogyne hapla. The orf2 expression product was not detected by SDS-PAGE, but its mRNA was detected by RT-PCR. The orf2 coexpressed with orf1 at a high level in the absence of the inverted-repeat sequence, whereas, the expression level of orf1 was decreased. When orf2 was mutated, the level of orf1 expression was enhanced obviously. In conclusion, the inverted-repeat sequence disturbs orf2 expression, and the orf2 downregulates orf1 expression. This is an example of novel negative regulation in B. thuringiensis and a potential method for enhancing the expression level of cry genes. |
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